Novel high temperature resistant fabrics

ABSTRACT

A novel open weave fabric is disclosed which comprises in a leno weave, warp yarns of polyamide fiber and crossover yarns of polyamide fiber braided over a core of glass fibers and/or metal wire. The fabric weave is then finished with a coating of a high temperature resistant resin selected from polyamides, polyimides, polyamide-imide or derivatives thereof. The fabric of the invention is useful for fabricating conveyor belts employed in conveying textiles through dryers and in like applications.

Elite States Patent [1 91 Romanski et al.

[ Mar. 18, 1975 1 NOVEL HIGH TEMPERATURE RESISTANT FABRICS [75]Inventors: Eric R. Romanski, Delmar; J. Drew Horn, Kinderhook; WilliamH. Dutt, Rensselaer, all of NY.

[73] Assignee: Albany International Corporation,

Albany, NY.

22 Filed: Nov. 30, 1973 21 App1.No.:420,431

[52] U.S. Cl. 161/88, 28/74 R, 28/75 R, 4/232, 74/239,161/89, 161/91,161/92, 161/93,161/175,161/227 [51] Int. Cl. B32b 5/02, D03d 19/00 [58]Field of Search 161/88, 89, 90, 91, 92, 161/93, 175, 227, 146; 28/74 R,75 R;

117/128, 128.4, 138.8 N, 161 P; 139/383 R,

[56] References Cited UNITED STATES PATENTS 2,679,677 6/1954 Crandall161/90 3,595,730 7/1971 Richardson 161/89 Primary Examiner-Marion E.McCamish Attorney, Agent, or Firm-Kane, Dalsimer, Kane, Sullivan &Kurucz [57] ABSTRACT 11 Claims, No Drawings NOVEL HIGH TEMPERATURERESISTANT FABRICS BACKGROUND OF THE INVENTION 1. Field of the InventionThe invention concerns high temperature resistant synthetic fabrics andmore particularly concerns a high temperature resistant, coated openweave fabric and dryer belts made therefrom.

2. Description of the Prior Art The requirements for dryer belts havebecome more and more demanding as the textile industry continues toevolve. The demand for higher temperature drying ovens, faster machinethroughputs, and more complete solvent recoveries to meet pollutionrequirements in the textile industry have' created a demand for dryerbelts which will tolerate the more severe conditions without asignificant reduction in operating life.

Prior hereto, metal mesh belts have been employed as dryer belts intextile dryers. However, the metal belts exhibit poor flex fatigueresistance and track poorly, particularly when run at high speeds. Also,over a relatively short period of time, small wire strands break andbend leaving a sharp point which will catch and damage the textile beingconveyed.

Synthetic belts employed previously have included, for example,fiberglass fabrics coated with polytetrafluoroethylene. These syntheticfabrics generally enjoy short lives as dryer belts, having a relavitelypoor resistance to abrasion, relatively low strength and poor trackingability at high speeds.

Open weave nylon Fourdrinier wires have been employed extensively inpapermaking, particularly nylon fabrics coated with phenolic-aldehyderesins (see for example, U.S. Pat. No. 3,032,441). Although such fabricsare excellent in terms of their durability and long life they generallyhave low air permeability and therefore are oflimited value where a highvolume of air passage is desired (as is the case of dryer belts for thedrying of textiles).

We have found that a particular open weave, employing particular warpand weft yarns and coated with particular types of resin compositionsyield fabrics particularly valuable for dryer belts. The dryer beltsfabricated from the fabric of the invention show high temperatureresistance, dimensional stability in spite of a very open weave, highair permeability, excellent tracking characteristics at high speeds anda high degree of abrasion resistance. Surprisingly, these advantageousproperties are obtained in a fabric product which is substantiallylighter and more flexible than fabrics previously employed to fabricatedryer belts. One would not ordinarily expect to obtain longer life andbetter durability in the lighter dryer belts of the invention.Furthermore, the light weight and better flexibility of dryer beltsfabricated from fabrics of the invention provide for easy installationon existing textile dryers. The heavier prior art dryer belts aregenerally more difficult to install.

SUMMARY OF THE INVENTION The invention comprises a high temperatureresistant, open weave fabric which comprises; in a leno weave, (i) warpyarns comprising a high temperature resistant polyamide fiber and (ii)crossover yarns which comprise a high temperature resistant polyamidefiber braided over a core selected from glass fiber, metal wire andmixtures thereof; said weave being coated with'a high temperatureresistant resin selected from tures thereof. The fabrics of theinvention are especially useful as dryer belts and the invention alsocomprises dryer belts fabricated from the fabrics of the invention.

The term high temperature resistant" as used herein means an ability towithstand temperatures of from about F. to at least about 350 F. Certainembodi ments of the invention will withstand temperatures of at leastabout 500 F. without substantial degradation and are preferred forapplications where the higher temperature resistance is required.

DETAILED DESCRIPTION OF THE INVENTION The fabrics of the invention areprepared according to the process of the invention by weaving the warpand crossover yarns in a leno weave and then coating the woven fabricwith a high temperature resistant resin composition as specified ingreater detail hereinafter. The woven fabric will have an average yarncount of 6 by 5 per square inch.

The warp yarns may be any multifilament polyamide yarn prepared forexample from fibers of nylons such as nylon 6; nylon 6,6; nylon 6,10;nylon 11 and the like. Particularly preferred for the higher temperatureapplications are yarns prepared from aromatic polyamides and mostpreferred are yarns prepared from fibers of the polyamide polymer ofm-phenylenediamine and isophthaloyl chloride. Such fibers are well knownas is their preparation and the preparation of multifilament yarnstherefrom.

In general, the warp fibers have a denier in the range of from about 840to about 1,680 and preferably within the range of from about 840 toabout 1,260. The warp yarns advantageously have a breaking strength ofbetween about 40 to about 20 lbs. (min.) and preferably between about 30to about 25 lbs. (min.). An elongation of between about 10 percent to 7percent at 3 gms. per denier is most advantageous for polyamide fibersemployed in the warp yarns.

The crossover yarns are prepared by braiding a polyamide fibermultifilament yarn, such as one within the scope ofthose described abovefor the warp yarns, over a core material. Preferred as the polyamidefiber in the crossover yarn is the fiber obtained from the polyamidepolymer of m-phenylenediamine and isophthalyol chloride and mostpreferred is such polyamide fiber having the breaking strengths,elongation and denier set forth above as advantageous for the warpyarns.

The core materials used in the crossover yarns may be glass fibers,individually or in a bundle, such as B glass, E glass and like fibers;metal wire such as chromel R, Rene 41, Halstelloy B, phosphorous bronzeand the like; and combinations of the above. Preferred as the corematerial is a bundle of fiberglass (multiple glass fibers) with a singlestrand of phosphorous bronze wire. The fabrication of such compositeyarns is well known in the art and need not be discussed here.

The woven fabric is coated by any conventional means of coating fabricswith a resin such as by dip ping, spraying or doping with a hightemperature resistant resin composition hereinafter described. Thecoatstability to the fabric by bonding the warp and weft yarns togetherat the crossover points.

The amount of resin applied is generally not critical, however, thefabrics of the invention advantageously are coated with resin in aproportion such that the fabric weight is increased by from about 5percent to about 100 percent. Thus, the fabric of the invention has aweight of which from 2.5 to 50.0 percent comprises resin weight.Preferably the proportion of resin is such that the weight of the wovenfabric is increased by from about 5 percent to about 30 percent. Thus,the preferred fabrics of the invention have a weight of which from 2.5percent to percent comprises resin weight.

The resin coating employed may be any high temperature resistant resincoating composition selected from solutions, mixtures or dispersions ofa polyamide, polyimide, polyamide-imide resin and mixtures thereof.

More specific examples of the resin coatings employed to make the coatedfabrics of the invention are, forexample, the coating compositions ofpolyamide acids which upon curing yield a polyimide coating or apolyamide-imide coating (see for example U.S. Pat. Nos. 3,179,633;3,179,634; 3,518,219; 3,541,036; 3,546,152; 3,652,500 and 3,702,788disclosing such polyimide and polyamide-imide forming coatingcompositions).

Polyamide coating compositions such as nylon coatings are generally wellknown, such as for example the copolymers of nylon 6, nylon 6,10 andnylon 6,6 dissolved in organic solvents such as aliphatic alcohols andmixtures of aliphatic alcohols with water.

Preferred resin coatings for preparing the fabrics of the invention arethe polyamide-imide polymers, more particularly described aspolytrimellitamides, being prepared by the reaction of aromatic diamineswith aryl halide derivatives of trimellitic anyhdrides. The methods oftheir preparation are well known; see for example the methods of US.Pat. Nos. 3,049,518 and 3,260,691. Coating compositions of the preferredpolytrimellitamide are generally well known and are commerciallyavailable (see for example the compositions of polytrimellitamidepolymer enamel described in US. Pat. No. 3,451,848).

In addition to the high temperature resistant resin applied as a coatingto the woven fabric, other conventionally employed coating materials maybe applied concurrently with the high temperature resin or in a separatetreatment. For example, silicone compounds may be advantageously appliedseparately or concurrently with application of the high temperatureresistant resin coating to enhance release characteristics of thefabrics of the invention. Such silicone compounds for enhancing releasecharacteristics of synthetic fabrics are well known and are commonlyemployed in textile finishes.

The following examples describe the manner and process of making andusing the invention and set forth the best mode contemplated by theinventors of carrying out the invention, but are not to be construed aslimiting.

EXAMPLE 1 A. Weaving of Fabric A 2 ply, 1,200 denier continuous filament(weighing circa 0.101 gms. per 30 inches) obtained from a polymer ofm-phenylenediamine and isophthaloyl chloride (Nomex, E. I. DuPont deNemours and Co., Wilmington, Delaware) and comprised of 9.95 twistsingles and 9.95 twist ply, the finished yarn having a tenacity of 5gms. per denier and an elongation of 8 percent at 3 gms. per denier anda weight of 397 grams per 100 yards, is woven as the warp with a fillingyarn of 4 end braid of 1,200 denier continuous filament obtained fromthe same yarn described above for the warp, braided over a coreconsisting of a bundle /1 fiberglass with a single strand of 0.008 inchdiameter phosphorous bronze wire. The warp yarns are spaced in fivegroups of two yarns each per inch and woven on inverted doup lenoharnesses to produce a half-twist between each crossover yarn insertion.The crossovers are inserted at six yarns per inch. The weight of thewoven fabric is about 1.36 ounces per square foot.

B. Coating of the Fabric A treating solution is made by diluting a 30percent solution of the polytrimellitamide polymer obtained by reactionof p,p-diaminodiphenylmethane with trimellitic anhydride acid chloridein N-methylpyrrolidone (AI 1030, Amoco Chemicals Co., Chicago, Illinois)with sufficient N-methylpyrrolidone to obtain a polymer concentration ofabout 10 percent by weight. The fabric of Part A, supra, is impregnatedwith the treating solution so as to increase the fabric weight by 10percent, after drying and curing the resin impregnated fabric. Aftertreatment with the resin solution, the wet fabric is dried for about 15minutes at a temperature of 400 F. and then cured for about 15 minutesat a temperature of about 450 to 500 F.

The coated fabric obtained above is found to have a breaking strength of245 lbs. per linear inch as determined by the method of ASTM D-1682-64,an elongation of 0.4 percent at 10 lbs. per linear inch loading asdetermined by ASTM D-1682-64 and an abrasion resistance of 1.95 percentloss of weight after 500 cycles as per ASTM-D-l175-64T (rotary drummethod). The fabric has a projected open area of 66.6 percent.

EXAMPLE 2 Following the procedure of Example 1, supra, a fabric of theinvention is prepared having a length of 133.3 feet, a width of 94.5inches, a weight of 87.9 lbs.; a breaking strength of 245 lbs. per inch(ASTM D-1682- 64) and a projected open area of 66.6 percent. The fabricis joined at the ends by a fold-back pin seam to make an endlessconveyor belt. The belt is easily installed in a tenter oven to supportknit fabrics during heat setting. The belt operates at speeds of circayards per minute and at temperatures of between 350400 F. The belttracks well, shows excellent dimensional stability and is highlyresistant to abrasion. In particular, the belt shows excellent abrasionresistance on the edges, in contrast to open weave fiberglass beltscoated with polytetrafluoroethylene which abrade on the edges whileoperated under the same conditions. The belt of this example also showsbetter dimensional stability, strength and track in comparison to thefiberglass belts coated with polytetrafluoroethylene. In comparison to astainless steel wire belt, the belt of this Example 2 shows a betterflex fatigue resistance and improved tracking characteristics.

What is claimed is:

l. A high temperature resistant open weave fabric which comprises:

in a leno weave,

i. warp yarns comprising a high temperature resistant polyamide fiberand ii. crossover yarns which comprise a high temperature resistantpolyamide fiber braided over a core selected from glass fiber, metalwire and mixtures thereof; said wrap yarns and said crossover-yarns ofsaid weave being coated with a high temperature resistant resin selectedfrom polyamides, polyimides, polyamideimides and mixtures thereof.

2. A fabric according to claim 1 wherein said warp yarns are polyamidefibers obtained from polyamide polymers of m-phenylenediamine andisophthalyol chloride.

3. A fabric according to claim 1 wherein the polyamide fiber of saidcrossover yarns is obtained from the polymer of m-phenylenediamine andisophthalyol chloride and the core of said crossover yarns comprisemultiple glass fibers and a single strand of metal wire.

4. A fabric according to claim 3 wherein said metal wire is aphosphorous bronze wire.

5. A fabric according to claim 1 wherein said resin is apolyamide-imide.

6. A fabric according to claim 5 wherein said resin is apolytrimellitamide.

7. A fabric according to claim 5 wherein said resin is the reactionproduct of p,p'-diaminodiphenylmethane and trimellitic anhydride acidchloride.

8. A fabric according to claim 1 wherein said coating comprises from 2.5percent to 50 percent of the weight of said fabric.

9. A fabric according to claim 1 wherein said coating comprises from 2.5percent to 15 percent ofthe weight of said fabric.

10. A fabric according to claim I wherein said polyamide fibers (i) and(ii) have a denier of from about 840 to about 1,680, a breaking strengthof between about 40 to about 20 lbs. (min.) and an elongation of iv. theends thereof joined together.

l l l

1. A HIGH TEMPERATURE RESISTANT OPEN WEAVE FABRIC WHICH COMPRISES: IN ALENO WEAVE, I. WARP YARNS COMPRISING A HIGH TEMPERATURE RESISTANTPOLYAMIDE FIBER AND II. CROSSOVER YARNS WHICH COMPRISE A HIGHTEMPERATURE RESISTANT POLYAMIDE FIBER BRAIDED OVER A CURE SELECTED FROMGLASS FIBER, METAL WITE AND MIXTURES THEREOF; SAID WRAP YARNS AND SAIDCROSSOVER YARNS OF SAID WEAVE BEING COATED WITH A HIGH TEMPERATURERESISTANT RESIN SELECTED FROM POLYAMIDES, POLYIMIDES, POLYAMIDEIMIDESAND MIXTURE THEREOF.
 2. A fabric according to claim 1 wherein said warpyarns are polyamide fibers obtained from polyamide polymers ofm-phenylenediamine and isophthalyol chloride.
 3. A fabric according toclaim 1 wherein the polyamide fiber of said crossover yarns is obtainedfrom the polymer of m-phenylenediamine and isophthalyol chloride and thecore of said crossover yarns comprise multiple glass fibers and a singlestrand of metal wire.
 4. A fabric according to claim 3 wherein saidmetal wire is a phosphorous bronze wire.
 5. A fabric according to clAim1 wherein said resin is a polyamide-imide.
 6. A fabric according toclaim 5 wherein said resin is a polytrimellitamide.
 7. A fabricaccording to claim 5 wherein said resin is the reaction product ofp,p''-diaminodiphenylmethane and trimellitic anhydride acid chloride. 8.A fabric according to claim 1 wherein said coating comprises from 2.5percent to 50 percent of the weight of said fabric.
 9. A fabricaccording to claim 1 wherein said coating comprises from 2.5 percent to15 percent of the weight of said fabric.
 10. A fabric according to claim1 wherein said polyamide fibers (i) and (ii) have a denier of from about840 to about 1,680, a breaking strength of between about 40 to about 20lbs. (min.) and an elongation of between about 10 percent to 7 percentat 3 gms. per denier.
 11. An endless dryer belt which comprises a hightemperature resistant leno weave fabric having i. warp yarns comprisinga high temperature resistant polyamide fiber; ii. crossover yarns whichcomprise a high temperature resistant polyamide fiber braided over acore selected from glass fiber, metal wire and mixtures thereof; iii. acoating on said warp yarns and said crossover yarns of a hightemperature resistant resin selected from polyamides, polyimides,polyamides-imides and mixtures thereof; and iv. the ends thereof joinedtogether.